In recent years there have been numerous advances in the level of understanding of how cancer cells grow inside a host. Generally, it is known that where a tumor or cancer becomes manifest, there is either a deficiency in the host's immune system and/or the tumor cells secrete or express agents which block the normal response of the host's immune system. In any event, there is a failure on the part of the host's immune system to recognize the presence of the cancer cell as "non-self". Because of this failure, the tumor cell and its progeny are allowed to grow without the benefit of predatory attack from the cells of the host's immune system which are normally responsible for detection of abnormal conditions. Primarily, the immune cells responsible for such predatory attack are the white blood cells of the CD34 lineage including the lymphocyte-activated killer macrophages and the T8 killer cells. Cells derived from CD34 lineage naturally become differentiated to ten or more mature cell types dedicated to specific functions. The functionality is believed to be determined by factors, such as cytokines, leading to the next differentiated stage.
Although seemingly much is known of specific hematopoietic cells which have become differentiated into identifiable discrete cell types, little is known about the physiologic control mechanisms involved in such differentiation process. Thus, contemporary research has centered primarily on examination of specifically known cell types and the cell surface "markers" recognizable at each such differentiation stage. Conspicuously lacking in the art has been clearly useful information or understanding of physiological events taking place within the cells as they metamorphosized from one state to the next differentiated state.
Consistent with the current state of understanding such cell differentiation is the methodology utilized by leading physicians and researchers in treatment protocols for cancerous diseases. Over the past several decades, cancer treatment methodologies have centered on conventional therapies such as surgical excision, radiation, and the injection of potent chemical agents. Such methodologies have well recognized limitations and have, in many cases, been proved to cause much additional pain and suffering to the patient as well as unreliable long-term effectiveness.
Numerous recent treatments have attempted to affect tumor cells by direct manipulation of cells understood to be active in clearing the body of dead or improperly functioning cells. Understandably, the cells targeted for investigation have involved cells of the immune response system. However, recent attempts at blocking growth of tumor cells, though utilizing sophisticated methodologies, such as by attempting to block the immune suppression capacity of the tumor cells, have generally been unsuccessful. These attempts are still ongoing and are also of questionable benefit in brining about reliable treatments resulting in long-term tumor remission.
Examples of methodologies in the recent art include targeted radiation and chemotherapy, injection of cytokines, injection of monoclonal antibodies to specific known tumor cell surface markers, and genetic therapies involving transforming cells with genes encoding factors believed to affect specific tumor states. One methodology has involved utilizing a class of natural immunostimulatory agents, particularly lymphokines, which are known to act as immunomodulators. Some lymphokines are produced by one T lymphocyte but act by signaling other T lymphocytes. Prior attempts have been disclosed in the art to regulate such immunomodulators by adding factors, such as Interleukin 2 (IL2), to enhance or elicit an immune response to tumor cells and thereby trump the immunosuppression effect that many tumor cells exhibit. The difficulty with such past investigations directed at blocking immunosuppression is that they have either failed entirely or have only attacked specific antigenic markers produced by the tumor cells. Other methods of treatment have included direct injections of various cytokines. Still other methods have attempted stimulating the patient's immune response cells using cytokines in the presence of the patient's own cancer cells, then reinjecting the treated immune response cells. A number of attempts have been made along these lines and a significant percentage of the patients do not respond optimally to such interventions.
The results of treatments utilizing any of the above methods indicates that subpopulations of cancerous cells remain undetected and unaffected and are able to present later clinical manifestation of the cancerous state. For example, a number of very malignant cancers, such as glioblastoma multiforme, continue to be a death sentence prognosis for patients who are so afflicted. Virtually all patients relapse, even after conventional debulking, chemotherapy and radiation therapy. Typical survival after diagnosis is usually 18 months. Other regiments include gene therapy. For example, when TGF-.beta. detection gene is inserted into a host's tumor cells in vitro, then injected to attempt to elicit an immune response, treatments are only temporarily successful and fail to provide a lasting benefit, even when combined with IL-2 co-stimulatory regimens. The reason is that not all of the tumorous cells have been eliminated because populations of tumor cells are heterogeneous in the variety of surface markers they present. Not all such markers will be available for presentation to cells responding to the protective response effects of TGF-.beta. or IL-2. Thus, some cells are not properly recognized in the treatment regime and survive undetected.
There is therefore an ongoing need for a means of stimulating more effectively and completely the host's immune response to serious disease and cancer states. The current invention has centered on the recognition that dendritic cells derived from precursor CD34 stem cells may be specifically directed to become a programmable antigen presenting cells (pAPCs). The current invention shows that in fact the pAPCs may indeed be programmed to become programmed super presenting cells (pSAPCs) having the capacity to elicit an immune response to any number of tumor antigen moieties after being "loaded" with either tumor derived RNA in toto or the poly A+ population thereof, or with the expressed proteins encoded by such RNAs including immune significant tumor antigens expressed therefrom.
It will be well appreciated in the hemopoietic cell art that dendritic cells are typically marrow-derived leukocytes which are known to play a central role in cellular immune responses. There are many aspects of dendritic cell ontogeny which remain poorly defined. However, most studies suggest that these dendritic cells emerge from the bone marrow, circulate in the peripheral blood in an immature form, and then enter tissues where they fuinction as an antigen-presenting cell. Once these dendritic cells capture a foreign body or some type of cell recognized as non-self, they then migrate to central lymphoid organs where they present these antigens to the T lymphocytes. Once the dendritic cell makes the presentation to the T lymphocytes, the T lymphocytes then mount an immune response.
Dendritic cells are difficult to study due to the scarcity of their populations and difficulty in growing these cells in cell culture. Dendritic cells can be derived from three readily available sources: (1) peripheral blood monocytes, (2) bone marrow and (3) umbilical cord blood. The functional differences between dendritic cells which are derived from the peripheral blood monocytes and those derived from bone marrow remain controversial. Dendritic cells possess ideal characteristics to be used as antigen-presenting cells. The key problems experienced by researchers has been both the inability to retrieve dendritic cells in sufficient quantity and to direct a stem cell to develop into a dendritic cell either in sufficient quantity or sufficient specificity. Therefore, if dendritic cells could be properly propagated and channeled, the fact of their possessing ideal characteristics to generate a tumor-specific cellular immune response by processing and presenting tumor-associated antigens to primed CD4+ T lymphocytes, they would serve as a highly desirable and efficient means to initiate an immune response.
Moreover, the current state of the art in cancer research has focused on the science of recombinant DNA sequencing. In general, researchers are searching the genomes of cells for DNA sequences encoding genes responsible for causing either the cancerous state itself, or the cancer's immunosuppressive effects. At least 6,000 genes have been identified and characterized. The human genome itself is estimated to harbor at least 100,000 genes. Additionally, it is believed that any given cell may express 20 to 45 thousand different genes during its life cycle if not at one time. Cancer cells are believed to express numerous genes in addition or in lieu of those normally expected to be expressed and in fact may express a greater number than the average normal cell.
Heretofore, researchers have focused on identifying various unique genes such as Her2neu or Brac-a, and have associated such specific genes with specific cancers. Unfortunately, by focusing on single genes so associated with a cancer, the possibility, and even probability, that such genes may have little significance with respect to an immunological response is lost. The reason that such single genes may not be all important to the cancer state and immune response is that such cancer cells are heterologous, not homologous, with respect to expression of surface antigen markers.
The present invention furthers the state of the art by making it clear that it is not significant to identify every single gene that is expressed on a cancer cells. Rather, that it is important to provide a means by which the expressed genes of a cancer cell may be presented along with, or in combination to, the immune response system by a means directly useful to the "natural" mechanisms of recognition utilized by immune system cells. The inventors of the present invention delineate how this may be accomplished by directed growth of dendritic cells to a state where they may become programmable antigen-presenting cells, or pAPCs, capable of digesting a foreign cell (non-self), or ingesting foreign cell RNA in toto or as the poly A+ portion thereof, or the expression product encoded by such RNAs. The inventors intend for the pAPCs to select appropriate cancer RNA or RNA expression products to be most appropriate for presentation for the fact of such RNAs and expression products being recognized as nonself.
Although a similar digestion of nonself matter occurs in the natural setting with the aid of macrophages and other phagocytotic cells, the present invention avoids the conditions understood to occur in vivo and accomplishes enhanced digestion and presentation in vitro. The current invention provides for uniform conditions under which dendritic cells may be directed or evolved to a state where they may be highly effective in digesting and/or selecting appropriate cancer and other cell markers for presentation. The inventors hereby suggest that during the digestion process, the dendritic cell will itself identify those "RNA" antigens of significance for the immune system meaning that it will select out some 10 to 20 or more antigens from a specific cancer cell, RNA, or RNA encoded product which have immunological significance. Under in vivo conditions of a host afflicted with a cancer, such selection may not be effectively recognized by the immune system, especially one that is compromised or masked. In contrast, under conditions of the current invention, the dendritic cell selected markers may be presented to T4 and T8 cells in an environment which will allow such T4 and T8 cells to become properly educated and activated so as to trigger a useful immune response.
The current invention provides a means by which the dendritic cell can be activated to become a "programmable" antigen-presenting cell or pAPC which is a "manufactured" dendritic cell line and which can further be "immortalized". Immortalization of the pAPC allows for a suitable continuous source of cells which may comprise the basis of an allogenic vaccine. Therefore, the donor host or any host of the same allotype with the same disease, exhibiting such RNA in toto or poly A+ portion thereof, or the encoded protein therefrom, with this source of allogenic dendritic cells will create vaccines directed to particular tumors. Similarly, these allogenic dendritic cells may be mixed with representative samples of different tumors' RNAs or RNA encoded products. For instance, the current invention contemplates combining a plurality of tumor's RNAs and/or RNA expression products from progressive stages of the same cancer type. By representing differentiation periods in the disease progress, a heterogeneous population of tumor cell antigens are presented to the pAPC and therefore a single vaccine may be created representing "different phases" of the cancer giving rise to a multivalent vaccine. Therefore, one vaccination using such an allogenic-based vaccine may protect against the whole spectrum of a specified cancer. Similarly, an allogenic vaccine for one very poorly differentiated cancer with many atypical features may also have an effect on more early stages of the same type of cancer or a different cancer, meaning that a vaccine made from allogenic pAPCs to glioblastoma tumor tissue, or its RNA, or its RNA expression products for instance, may prove efficacious in use with other unrelated tumors such as a prostate cancer. The current invention further provides for "commonalities" between all cancers which makes possible a single allogenic vaccine that is effective for a multiple of different cancers. Thus, many features which are similar to all cancers may be provided for in a pSAPC for presentation to cells of the immune system, in effect providing immune-specific antigens with commonality between different tissue types.
The current invention also contemplates use in placing specific antigens on the pAPC which function in a regulatory surveillance mode to prevent recurrence of a new cancer or a heterozygous group of cancer cells from growing out of control. For example, a pAPC "programmed" for lung cancer may be used in effectively eliminating a host's cancer using an "autogenic" lung cancer vaccine. Where a sub-group of cells survive this immune response, because a heterozygous group of antigens is not recognized as that presented by the pSAPC, a different pSAPC with "memory" to capture di novo cancers may also be used to educate immune system cells. Such pSAPCs equipped with "surveillance antigens" may be effective not only against a heterozygous group of tumor antigens but may also be used for surveillance in di novo cancers separate from the original cancer for which the host was treated using the autogenic vaccine.